TED-ED VIDEO: Why are manhole covers round?

[Ryan Goble]

Why are manhole covers round? - Marc Chamberland Animation by Pew36 Animation Studios Why are most manhole covers round? Sure it makes them easy to roll, and slide into place in any alignment. But there’s another, more compelling reason, involving a peculiar geometric property of circles and other shapes. Marc Chamberland explains curves of constant width and Barbier’s theorem.  View full lesson »